The invention relates to an aircraft airfoil or lifting wing including at least one short-coupled or close-mounted engine, i.e. an engine mounted close to the wing on a short pylon, and including a high lift system provided at the leading edge of the airfoil. Particularly, the invention relates to a flap-like auxiliary high lift device adapted to be extended into an open space or gap in front of the leading edge of the airfoil, between the engine pylon, the outer lateral edge of a leading edge flap arranged on the inboard side of the pylon, and the portion of the airfoil leading edge nose extending between the pylon and the inboard leading edge flap. In this regard, and throughout this application, the extendable leading edge flap of the high lift system may be a slat, a Krueger device, a deflectable or bent nose device, or the like, for example.
Conventional aircraft typically use leading edge high lift devices to provide auxiliary lift in certain configurations and under certain flight attitudes. These leading edge high lift devices are aerodynamically effective movable components on the leading edge of the airfoil, such as slats, Krueger flaps, or the like, for example. The use of such leading edge high lift devices causes problems, however, at the areas where the engines are connected to the airfoil or wing. Namely, the size and position of the engine nacelle in relation to the airfoil limits either the size, the span-wise extension, and/or the adjustment and movement possibilities of such components. For example, if a prescribed depth of the leading edge high lift devices and a prescribed deflection angle are to be achieved for a landing configuration, then it is typically necessary to reduce the spanwise extension or length of the high lift devices, to prevent a collision between these devices and the engine nacelle or the engine pylon.
As a result of the above considerations, a portion of the airfoil leading edge cannot be used for increasing the lift. Namely, the above mentioned open space or gap between the side of the engine nacelle or pylon, the facing edge of the adjacent leading edge slat or other high lift device, and the leading edge of the airfoil extending therebetween, causes aerodynamic losses because the airflow through this open space or gap is not influenced in the desired manner by the leading edge high lift device. To address this problem, various complicated detail solutions have been provided, for example as follows.
One known system has been disclosed in German Patent 197 43 907, which issued Dec. 10, 1998 to the same assignee as the present application. That known system according to German Patent 197 43 907 involves an auxiliary device in the form of an additional, separately controllable and movable leading edge flap or slat device that can be slidingly or tiltingly extended out of the wing contour into the above mentioned open space or gap. While such an auxiliary device is very effective in closing the gap, or particularly achieving improved aerodynamic conditions in the area of the gap, it has been found to require relatively substantial efforts with regard to the mechanics that are necessary for realizing such a leading edge auxiliary device arrangement. Thus, it is considered that a simplification of such a device or system would be desirable.
Another attempted solution of the above discussed problems is the provision of a leading edge auxiliary lift device that extends completely along the entire span width of the airfoil, with a clearance opening or so-called xe2x80x9cnotchxe2x80x9d provided to create a free clearance space between the pylon contour and the engine contour. In this context, the free clearance space of the span-wise extending auxiliary flap part, for example the span-wise end part of a leading edge slat extended on the inner side of the engine pylon, must be adapted to accommodate the greatest deflection or extension of the flap part, i.e. the landing configuration. For this reason, accordingly, the effectiveness of such an auxiliary lift system is disadvantageously reduced with smaller deflections, for example in a take-off configuration.
U.S. Pat. No. 4,540,143 (Wang et al.) discloses an engine-wing arrangement in which the nacelle of the engine comprises air flow guide surfaces on its outer contour. These guide surfaces serve to influence a turbulent air flow that is generated at the upper front nose or leading edge of the nacelle and then flows over the upper surface of the airfoil.
In view of the above it is an object of the invention to provide an arrangement of the above described general type, that is improved in such a manner so as to achieve a substantial reduction of the construction effort and complexity, the weight, and the construction costs of such a system in comparison to the previously proposed arrangements. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as are apparent from the present specification.
The above objects have been achieved in an airfoil arrangement according to the invention including an airfoil, an engine, a pylon connecting the engine to the airfoil, a leading edge high lift device movably connected to the airfoil at a leading edge thereof, and an auxiliary high lift device. An open space is formed between the leading edge of the airfoil, the pylon, and a side edge of the leading edge high lift device facing the pylon. The auxiliary high lift device is movable so that it can be extended into an extended position in which the auxiliary high lift device is positioned in the open space between the pylon, the airfoil leading edge, and the side edge of the leading edge high lift device. Particularly according the invention, the auxiliary high lift device is embodied as a movable flap-like component or xe2x80x9cnacelle doorxe2x80x9d which can be retracted into a retracted position in which it is recessed and integrated into the outer contour of the engine nacelle and/or the pylon. Preferably, the auxiliary high lift device is also movably, mechanically connected to the engine nacelle and/or the pylon so as to be extendable therefrom. In the extended position, the auxiliary high lift device aerodynamically closes or covers the open space or gap. Preferably, the auxiliary high lift device is profiled or contoured in such a manner so that the maximum lift and the critical angle of attack of the airfoil are increased.